1. Field of the Invention
The present invention relates generally to landing gear actuators and, more particularly, to a pneumatically powered landing gear actuator.
2. Description of the Prior Art
In tractor-trailer combinations, the trailer typically includes a pair of landing gear feet which extend downwardly from the bottom and near the front of the trailer. In the well known fashion, the landing gear feet contact the ground and support the trailer in an elevated position when the trailer is detached from the tractor. Conversely, when the trailer is attached to the tractor, the landing gear feet are retracted or raised from the ground to prevent interference between the ground and the landing gear feet while the trailer is being transported by the tractor.
Many of the previously known landing gear feet are both vertically extendible and retractable within landing gear assemblies attached to the bottom of the trailer. While the landing gear assemblies vary in internal design from one to another, most include a rotatable input member, the rotation of which extends or retracts the landing gear foot in dependence upon the direction of rotation of the rotatable input member.
The previously known input members are typically rotatably driven by a hand crank manually operated by the truck driver. Such hand cranks are advantageous due to their low cost, but are disadvantageous in that the hand cranks are not only time consuming in use but also tend to physically exhaust the truck driver or operator.
In order to overcome the above-mentioned disadvantages associated with manually operated hand cranks, several of the previously-known landing gear assemblies have included hydraulic motors drivingly connected with the input member of the assembly and fluidly coupled to the hydraulic system of the tractor. These previously-known hydraulic motors, however, are very expensive to construct and install in the landing gear assemblies and are also prone to failure. Moreover, such hydraulic motors require a source of hydraulic pressure which, in many cases, is unavailable. Pressurized air, on the other hand, is utilized to operate the brake systems of tractor-trailer combinations and thus a source of such air is readily available to operate the landing gear.